The B. subtilis phage SP-15 contains DNA with unusual and unique properties. This is due mainly to the presence of the unusual pyrimidine dihydroxypentyluracil (DHPU) which in turn has phosphorylated sugar residues attached to the hydroxyl groups its side chain. In collaboration with Dr. Nakanishi of Columbia University, current and proposed research will deal with the configuration of the sugar residues and the nature of their attachment to DHPU. Experiments are also being planned to study the biological precursor to DHPU in SP-15 B. subtilis cells. Studies on the configuration of the DHPU should be helpful in predicting what the precursors might be. Using labelled material, predictions could then be verified. Studies on the properties of SP-15 DNA in phage infected cells will be continued. The modifications of phage DNA (e.g., removal of sugar phosphate from parental infecting phage DNA) may represent important new controls in phage DNA transcription and replication. The initial in vivo and in vitro observations that following SP-15 infection a phage specific enzyme is made that cleaves a sugar(s) phosphate from parental phage DNA will be followed up.